[ARC5] [Milsurplus] Radio on the Frontlines: WWI and WWII | DPLA

Tue Mar 10 01:29:27 EDT 2020

That’s a favorite book of mine. I love that story of “inverse capitalism”. Oops!

Tom

Sent from my iThing, so please forgive brevity and typos

> On Mar 9, 2020, at 22:08, Dennis Monticelli <dennis.monticelli at gmail.com> wrote:
> 
> Parts of "Crystal Clear" are very interesting.  The part about mining in Brazil comes to mind.  At its peak there were about 50,000 natives involved in open pit mining.  Prior to the creation of these big mining operations individual natives would look for points much as a casual prospector would; to earn a little spending cash.  Local intermediaries would buy them when the native eventually came to town for supplies or other reasons.  The US wanted more material than was being gathered and like the true capitalists that we are we doubled the offering price with the high expectations of hauling in more rocks.  Well the natives weren't exactly card carrying capitalists.  With the price doubled they only had to find half the number to make enough money for whatever they were spending it on.  Supply dropped drastically.  Ooops.
> 
> Dennis AE6C
> 
>> On Mon, Mar 9, 2020 at 9:39 PM Dennis Monticelli <dennis.monticelli at gmail.com> wrote:
>> Temp comp when different masses are involved is always tricky.  It's in play with typical commercial boat anchors and affects mil gear as well.  The mass of a big old ceramic coil is far different than a relatively smaller cap...and who knows which is near that hot tube.  I'm sure users turned on equipment early and tried to stabilize it as much as possible.  
>> 
>> In Thompson's 2007 book, "Crystal Clear" the point is made about the utility of having precise frequency setting and being able to rapidly punch preset channels.  The example given is a tank engagement where different groups of tanks would be assigned different VHF frequencies and central command another.  In a tank battle seconds matter so rapidly and confidently changing channels in a vibrating tank is a major advantage while coordinating your attack/defense.  It's easy to believe that push button crystal control would beat the heck out of mechanical presets and manual fine adjustments.
>> 
>> Dennis AE6C
>> 
>> 
>> 
>> 
>> 
>>> On Mon, Mar 9, 2020 at 8:26 PM Tom Lee <tomlee at ee.stanford.edu> wrote:
>>> That agrees with what I was told at the Deutsches Museum. Does Trenkle 
>>> talk about this in one of his books?
>>> 
>>> -- 
>>> Prof. Thomas H. Lee
>>> Allen Ctr., Rm. 205
>>> 350 Jane Stanford Way
>>> Stanford University
>>> Stanford, CA 94305-4070
>>> http://www-smirc.stanford.edu
>>> 
>>> On 3/9/2020 20:17, Heinz Breuer wrote:
>>> > Hello Tom,
>>> >
>>> > the ceramic material either low T/C for coil forms and variable capacitors or with defined T/C for dogbone tubic style ceramic capacitors was a German innovation.
>>> > The capacitor plates for variable capacitors were made out of milled brass and silver plated.
>>> >
>>> > Tuned circuits were temperature compensated by dogbone tubic style ceramic capacitors available with different negative T/C specs.
>>> >
>>> > vy 73 Heinz DH2FA, KM5VT
>>> >
>>> > Von meinem iPhone gesendet
>>> >
>>> >> Am 10.03.2020 um 00:27 schrieb Tom Lee <tomlee at ee.stanford.edu>:
>>> >>
>>> >> I visited the Deutsches Museum in Munich a year or so ago (one of my favorite museums on the planet), and had a chance to speak with one of the docents who manned their amateur radio display. He claimed that their quartz-free WWII radios were stable to about 0.1% over temperatures encountered in the field (whatever that means). He could not cite any source for this claim, but offered plausible explanations. He said that the main bit of magic was pre-stressed inductor windings on low-TC coil forms (the coils were wound with heated wires which contracted upon cooling, so that the overall inductor TC was that of the form, not of the wire). Not as good as quartz, he admitted, but it mainly got the job done. I've heard of this pre-stressing method before, but this gentleman seemed to imply that it was a German innovation. I have no idea if that is in fact the case.
>>> >>
>>> >> --Tom
>>> >>
>>> >> -- 
>>> >> Prof. Thomas H. Lee
>>> >> Allen Ctr., Rm. 205
>>> >> 350 Jane Stanford Way
>>> >> Stanford University
>>> >> Stanford, CA 94305-4070
>>> >> http://www-smirc.stanford.edu
>>> >>
>>> >>> On 3/9/2020 16:02, Hubert Miller wrote:
>>> >>> Germany in the 1930s on had a limited supply of quartz. That didn't hobble their military communications; they compensated for this
>>> >>> with mechanical precision. I would say quartz frequency control didn't really become a requirement until most communications
>>> >>> migrated to VHF.
>>> >>> -Hue
>>> >>>
>>> >>>> I don't know where I read it, but I read that the use of crystals to control the transmitter's exact frequency (hence, you could have a
>>> >>> radio "channel") was what made radio go from an option for battlefield communications to a tactical advantage and communications
>>> >>> necessity. Someone please correct me if I am wrong, but I believe that was in the 1930's for military communications.
>>> >>> 73, Gordon KJ6IKT
>>> >>>
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